1. Field of the Invention
The instant invention relates to that field of devices consisting of articles of manufacture known as dowel pin hole drilling guides. Specifically, the instant invention is an adjustable dowel pin hole dring guide for drilling dowel pin holes along various horizontal planes in a work piece.
2. Background Information
The prior art known to applicant discloses that dowel pin dring guides are relatively well known within the art. These driling guides have ranged from the simple, as embodied in U.S. Pat. No. 2,798,520 issued to J. M. Maskulka on Jul. 9, 1957, to the more complex, as embodied in U.S. Pat. No. 5,954,461 issued to Raymond A. Lemieux on Sep. 21, 1999.
In Maskulka, the primary object of the invention was to create a drill guide which would allow a wood worker to assemble wooden frames without resorting to the traditional mortising of the joints. This was accomplished by creating a device which had an essentially "L" shaped body, the body having two tubular openings, the bore of the tubular openings passing completely through one "leg" of the "L" shaped body. The user of the device would simply lay the wood fame which was to be drilled so that it was cradled by the body, and the tubular openings aligned with the areas of the wood frame which were to be drilled.
This approach worked reasonably well for drilling the flattened ends of wood frames. However, as proposed by Maskulka, it was less than simple to use when drilling the ends of wood frames which were cut on an angle. To drill dowel pin guide holes on an angled end of a wood frame, the user was forced to carefully measure and locate a center line on both pieces of wood. If the center line was off even slightly on either piece, the two pieces would fit together unevenly, thereby negating the device's intended benefit. While this requirement of a carefully located center line applied even to the flat ended wood frame, Applicant believes it was less likely to cause serious errors as a piece of wood frame work which is composed entirely of 90 degree angles as it is much easier hold in place and measure than is one having more or less steep angles.
These limitations were overcome by my prior patent, U.S. Pat. No. 5,954,461 issued to Lenieux on Sep. 21, 1999. In Lemieux '461 the device is composed of a stable piece and a movable piece, the movable piece being pivotably attached to the stable piece such that the movable piece may be adjusted to permit the drilling of dowel pin holes into work pieces which have angled sections, the movable piece being adjusted to follow the angle of the work piece which is to be drilled.
Unfortunately, another inherent limitation of the art typified by Maskulka and present in Lemieux '461 as well was that it was nearly impossible to assure accurate placement of the dowel pin holes to be drilled in various horizontal planes which are not pre-set during manufacture of the devices. So long as the work piece to be drilled was a standard thickness, and the device disclosed by Maskulka was proportioned to that particular thickness work piece, the device worked as described. Furthermore, it is possible in Lemieux '461 to modify the length of the downwardly depending sections of the movable piece through which the attachment channels pass and or vary the placement of the attachment channels along the downwardly depending sections so that work pieces having a different thickness might be drilled. Unfortunately, a modification of this sort is a permanent one which must be made during the manufacture of the device.
In the event that work pieces having thicknesses which differ from one another are to be used, or in the event that the user of the device did not want the dowel pin holes placed along the same horizontal plane (the horizontal plane being dependent upon the distance between the surface of the dowel pin drilling guide device upon which the work piece was located when drilled, and the axis passing through the center of the dowel pin drilling guide hole), neither Maskula nor Lenieux '461 may satisfactorily be employed as the horizontal placement of the axis of each dowel pin guide passage is pre-set during the manufacture of the devices.
A further, and even more serious drawback to the Maskulka device was that it was practically useless when toying to place dowel pins into a wood frame which incorporated compound angles. For example, if one wished to construct a wooden cone using wood strips, it is necessary to include a compound angle along each side to be joined to another wood strip. The device described in the Maskulka patent cannot be used along such compound angles without a great deal of careful measurement and shimming prior to clamping the device to the wood strip. This limitation was overcome by the Lemieux '461 patent which provided a simple and efficient means for drilling dowel pin holes into work pieces having compound angles.
However, while Lemieux '461 permits the drilling of dowel pin holes into work pieces having compound angles, it is essentially just as limited as Maskulka when it comes to drilling dowel pin holes into work pieces of varying thicknesses which include compound angles. Neither Maskulka nor Lemieux '461 provide a simple and efficient means for drilling dowel pin holes into work pieces of varying thicknesses having compound angles or placing dowel pin holes along different horizontal planes in work pieces having compound angles.
Furthermore, Applicant has learned that it is often beneficial to be able to drill multiple dowel pin holes into a work piece along different horizontal planes. That is, even when working on a number of work pieces of identical thicknesses, it may be useful to be able to drill dowel pin holes not only along a horizontal plane which bisects the work piece, but also along various other horizontal planes above and below the bisecting horizontal plane. Maskulka simply cannot do this, and Lenieux '461 can do this in only a limited fashion, the limitation being the precise horizontal placement of the attachment channels, the horizontal location of the dowel pin drilling guide passages and the thickness of the stable piece. Once these three variables have been set during manufacture of the device, drilling along other various horizontal planes cannot be accomplished without a great deal of shimming of the work piece. And while shimming of the work piece is possible, it creates an even greater possibility for misplacement of the dowel pin holes as multiple work pieces are drilled, each requiring accurate and repeated shimming.
Shimming a work piece in order to modify the precise horizontal placement of the dowel pin guide hole is a simple enough matter when drilling only one work piece. However, most projects which require dowel pin holes usually also require that those dowel pin holes be drilled into more than one work piece. For example, when creating a square wood frame to encompass a picture, at least four pieces would be required. Each of these pieces would need to have dowel pin holes drilled into both ends. Therefore, if one were to attempt to drill the dowel pin holes along any horizontal plane other than that pre-set in the prior art devices, one would need to shim each work piece at least twice (once for each end). Furthermore, in order to ensure a proper fit, one would need to be absolutely certain that each work piece was shimmed in exactly the same maimer as each other work piece. Should the shimmy be off even slightly, the dowel pin holes which are drilled would not be properly aligned, necessitating extensive and burdensome surface preparations.